History of the Eye Chart

history eye-chart

Reading an eye chart mounted or projected on a wall is a standard part of every visit to the optometrist today, but it wasn't always that way. Centuries ago, practitioners struggled to measure visual acuity, the ability to see clearly. As a result, patients were given glasses that didn't adequately correct their vision. Nineteenth-century eye doctors realized that they needed a uniform way to test vision. After a little experimenting, they created eye charts that helped them quickly and accurately assess acuity.

A Man Ahead of His Time

German physician Heinrich Kuechler designed an early eye chart in 1843 that featured one word per line. Although the first word at the top of the chart was large, the typeface size became progressively smaller with each line. Three different versions of the Kuechler chart were used to prevent patients from memorizing the words. Unfortunately, others in the medical field did not share Dr. Kuechler's enthusiasm for the chart, and it was never used extensively.

The Introduction of the Modern Eye Chart

In 1854, Austrian ophthalmologist Eduard Jaeger developed a new chart designed to test acuity after cataract surgery. The chart was eventually also used to diagnose refractive errors, such as myopia (nearsightedness) or hyperopia (farsightedness). His chart didn't display a single word per line like Dr. Kuechler's chart but required patients to read a series of sentences printed in several sizes. Because the size of the letters varied based on the typeface that a particular doctor used, it was difficult to obtain uniform results with the Jaeger chart.

Franciscus Donders was one of the ophthalmologists who became frustrated by the limits of Dr. Jaeger's chart. Dr. Donders was studying accommodation, the eye's ability to change focus between near and far objects, and refraction, the way light rays bend when they pass through the eye. He realized that he needed a chart that would help him accurately measure both near and far vision and asked his colleague Herman Snellen to create a new eye chart in 1862.

Dr. Snellen's first attempt at chart design involved an array of shapes that he asked patients to describe. Unfortunately, everyone described the shapes a little differently, which affected the accuracy of the test. Snellen decided to use capital letters instead and created his very own characters, which were known as optotypes.

Optotypes were proportional and designed to be easily reproducible no matter where in the world the chart was used. The letters at the top of the chart were very large but gradually decreased in size. Patients stood 20 feet away from the chart and tried to read each of the 11 lines from top to bottom. Although Snellen's chart is still in use today, mirrors are often used to allow patients to read the chart from distances less than 20 feet.

Snellen also designed a special chart for young children or people who couldn't read. The chart uses a capital "E" turned in various directions and printed in decreasing sizes. During the eye test, patients are asked to describe which way the arms of the E are pointing.

Throughout the years, a few tweaks have been made to the Snellen chart. In 1868, Dr. John Green refined the grid, introduced proportional spacing and ensured that each line was 25 percent smaller than the one preceding it.

In addition to the Snellen eye chart, you may also read the Bailey-Lovey Chart during your visit to the eye doctor. The chart, which was created in 1976 to evaluate near vision, uses five letters per line and organizes the lines in a triangular shape. The chart features a logarithmic size progression to ensure that the only difference from line to line is the size of the optotypes.

How the Snellen Eye Chart Works

The Snellen eye chart helps optometrists identify a numerical representation of your visual acuity. For example, if you have 20/60 vision, the line that you can see clearly at 20 feet can be seen by someone with normal vision at 60 feet. If your vision is normal, you have 20/20 vision. Although reading the Snellen eye chart is the first step in determining your eyeglass or contact lens prescription, you'll also need a few other tests to fine-tune your prescription.

Has it been a while since you've seen a Snellen eye chart? Give us a call to schedule an eye exam.


American Academy of Ophthalmology: All About the Eye Chart, 11/30/16


New York Times: Who Made That Eye Chart?, 5/24/13


Gizmodo: Examining the Fascinating Typographic History of Eye Charts, 9/24/15


Medline Plus: Visual Acuity Test, 2/7/17



We look forward to hearing from you


Find us on the map


Reviews By Our Satisfied Patients

  • "Dr. Leek is very experienced and has a great kind, personality. I highly recommend him. His massage therapists are also great."
    Patricia K. / Grass Valley, CA

Featured Articles

Read about interesting topics

  • Nystagmus

    Nystagmus is a vision condition characterized by repetitive, uncontrolled eye movements. These involuntary eye movements may be side-to-side, up and down, or in a circular pattern, which hinders the eyes’ ability to focus on a steady object. Individuals with nystagmus may hold their heads in unusual ...

    Read More
  • Macular Hole

    The condition known as a macular hole refers to a tiny break in the macula that results in blurry or distorted vision. To fully understand the condition, one must understand eye anatomy. The macula is a spot located in the center of the retina (the back portion of the eye). Located where light comes ...

    Read More
  • How It Helps

    The goal of vision therapy is to treat vision problems that cannot be fully addressed through eyeglasses, contact lenses or surgery. For example, studies show that vision therapy may be beneficial for addressing eyestrain and other issues that can affect a child’s reading abilities. The human brain ...

    Read More
  • How It Works

    Vision therapy, also referred to as vision training, neuro-vision therapy, or vision rehabilitation, is an optometry subspecialty. Vision therapy is prescribed to develop, improve and/or enhance visual function so an individual’s vision system functions more smoothly. Vision therapy can be beneficial ...

    Read More
  • Age-Related Macular Degeneration

    One of the leading causes of vision loss in people who are age 50 or older is age-related macular degeneration (AMD). This common eye condition leads to damage of a small spot near the center of the retina called the macula. The macula provides us with the ability to clearly see objects that are straight ...

    Read More
  • Signs and Symptoms Checklist

    Vision therapy, which is also known as vision training or visual training, is an individualized treatment program that can help identify and correct perceptual-cognitive deficiencies that are impacting visual learning, focus, and concentration. Vision Therapy for Children: Checklist While individuals ...

    Read More
  • Pediatric Ophthlamology

    Ophthalmology addresses the physiology, anatomy and diseases of the eyes. Pediatric ophthalmology focuses on the eyes of children. Pediatric ophthalmologists examine children’s eyes to see if they need corrective lenses or other treatments to improve their vision. Training for Pediatric Ophthalmologists Pediatric ...

    Read More
  • Presbyopia

    Somewhere around the age of 40, most people’s eyes lose the ability to focus on close-up objects. This condition is called presbyopia. You may start holding reading material farther away, because it is blurry up close. Reading suddenly gives you eyestrain. You might wonder when manufacturers started ...

    Read More
  • Myopia

    Myopia, or nearsightedness, means that your eyes can see close objects clearly but struggle to see things in the distance. Nearly 30 percent of Americans are nearsighted. This condition usually develops in children and teenagers, up to about the age of 20. A teacher or parent might notice a child squinting ...

    Read More
  • Diabetic Eye Diseases

    Diabetes is a condition that involves high blood sugar (glucose) levels. This can affect many parts of the body, including the eyes. One of the most common diabetic eye diseases is diabetic retinopathy, which is also a leading cause of blindness in American adults. Diabetic Retinopathy Diabetic retinopathy ...

    Read More

Newsletter Sign Up